Dirt mitigation in a gas turbine engine

ABSTRACT

An aspect includes a dirt mitigation system for a gas turbine engine. The dirt mitigation system includes a plurality of bleeds of the gas turbine engine and a control system configured to determine a particulate ingestion estimate indicative of dirt ingested in the gas turbine engine. The control system is further configured to determine one or more operating parameters of the gas turbine engine and alter a bleed control schedule of the gas turbine engine to purge at least a portion of the dirt ingested in the gas turbine engine through one or more of the bleeds of the gas turbine engine based on the particulate ingestion estimate and the one or more operating parameters.

BACKGROUND

The subject matter disclosed herein generally relates to engine systemsand, more particularly, to a method and apparatus for dirt mitigation ina gas turbine engine.

Engines, such as gas turbine engines, can operate in uncleanenvironments that result in ingestion of dust, dirt, and debris.Particulate matter can accumulate within an engine as it operates over aperiod of time. The particulate matter can result in degradedperformance, such as thrust reduction, excess fuel consumption, andpossible component life reduction. Regular engine cleaning can removeenvironmental particulate matter; however, cleaning and servicing basedon a predetermined time interval may result in premature or late actionsrelative to the actual condition of an engine.

BRIEF DESCRIPTION

According to one embodiment, a dirt mitigation system for a gas turbineengine is provided. The dirt mitigation system includes a plurality ofbleeds of the gas turbine engine and a control system configured todetermine a particulate ingestion estimate indicative of dirt ingestedin the gas turbine engine. The control system is further configured todetermine one or more operating parameters of the gas turbine engine andalter a bleed control schedule of the gas turbine engine to purge atleast a portion of the dirt ingested in the gas turbine engine throughone or more of the bleeds of the gas turbine engine based on theparticulate ingestion estimate and the one or more operating parameters.

In addition to one or more of the features described above or below, oras an alternative, further embodiments may include where the particulateingestion estimate is determined based on a plurality of particle sensordata from the gas turbine engine.

In addition to one or more of the features described above or below, oras an alternative, further embodiments may include where the particlesensor data is received from one or more particle sensors at an inlet ofa low pressure compressor of the gas turbine engine downstream of a fanof the gas turbine engine.

In addition to one or more of the features described above or below, oras an alternative, further embodiments may include where the controlsystem is further configured to determine whether the particle sensordata indicates that a dirt concentration is above a threshold, an enginedeterioration is within a deterioration limit, and the gas turbineengine is within an operability limit prior to altering the bleedcontrol schedule.

In addition to one or more of the features described above or below, oras an alternative, further embodiments may include where the controlsystem is further configured to determine an amount of dirt in the gasturbine engine and determine an impact of dirt reduction associated withpurging at least the portion of the dirt ingested in the gas turbineengine.

In addition to one or more of the features described above or below, oras an alternative, further embodiments may include where the controlsystem is further configured to maintain the bleed control schedule tomaximize fuel economy based on determining that the dirt concentrationis below the threshold, the engine deterioration is outside of thedeterioration limit, or the gas turbine engine is outside of theoperability limit.

In addition to one or more of the features described above or below, oras an alternative, further embodiments may include where the controlsystem is further configured to perform one or more usage-based lifingcomputations to determine a dirt impact on the gas turbine engine andproject a next maintenance action needed for the gas turbine enginebased on the dirt impact.

In addition to one or more of the features described above or below, oras an alternative, further embodiments may include where the bleeds arebetween a low pressure compressor and a high pressure compressor of thegas turbine engine.

In addition to one or more of the features described above or below, oras an alternative, further embodiments may include where altering of thebleed control schedule is further based on one or more of: an ambientair temperature, an interstage turbine temperature, an exhaust gastemperature, a derate setting, and a thrust specific fuel consumption ofthe gas turbine engine.

In addition to one or more of the features described above or below, oras an alternative, further embodiments may include where the one or moreoperating parameters of the gas turbine engine include one or more of: aflight segment, a fuel consumption rate, and an operating margin of thegas turbine engine.

In addition to one or more of the features described above or below, oras an alternative, further embodiments may include where the particulateingestion estimate is determined based on a location of the gas turbineengine and an environmental parameter associated with the location.

In addition to one or more of the features described above or below, oras an alternative, further embodiments may include where the controlsystem is further configured to revert to a default bleed controlschedule of the gas turbine engine based on detection of a faultassociated with the dirt mitigation system.

According to another embodiment, a method of dirt mitigation in a gasturbine engine includes determining a particulate ingestion estimateindicative of dirt ingested in the gas turbine engine and determiningone or more operating parameters of the gas turbine engine. The methodalso includes altering a bleed control schedule of the gas turbineengine to purge at least a portion of the dirt ingested in the gasturbine engine through one or more bleeds of the gas turbine enginebased on the particulate ingestion estimate and the one or moreoperating parameters.

In addition to one or more of the features described above or below, oras an alternative, further embodiments may include where the particulateingestion estimate is determined based on a plurality of particle sensordata from the gas turbine engine, and the method further includesdetermining whether the particle sensor data indicates that a dirtconcentration is above a threshold, an engine deterioration is within adeterioration limit, and the gas turbine engine is within an operabilitylimit prior to altering the bleed control schedule. The method can alsoinclude determining an amount of dirt in the gas turbine engine anddetermining an impact of dirt reduction associated with purging at leastthe portion of the dirt ingested in the gas turbine engine.

In addition to one or more of the features described above or below, oras an alternative, further embodiments may include maintaining the bleedcontrol schedule to maximize fuel economy based on determining that thedirt concentration is below the threshold, the engine deterioration isoutside of the deterioration limit, or the gas turbine engine is outsideof the operability limit.

In addition to one or more of the features described above or below, oras an alternative, further embodiments may include performing one ormore usage-based lifting computations to determine a dirt impact on thegas turbine engine and project a next maintenance action needed for thegas turbine engine based on the dirt impact.

In addition to one or more of the features described above or below, oras an alternative, further embodiments may include reverting to adefault bleed control schedule of the gas turbine engine based ondetection of a fault associated with the dirt mitigation system.

A technical effect of the apparatus, systems and methods is achieved byproviding dirt mitigation in a gas turbine engine as described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

The following descriptions should not be considered limiting in any way.With reference to the accompanying drawings, like elements are numberedalike:

FIG. 1 is a partial cross-sectional illustration of a gas turbineengine, in accordance with an embodiment of the disclosure;

FIG. 2 is a schematic diagram of a dirt mitigation system, in accordancewith an embodiment of the disclosure;

FIG. 3 is a flow chart illustrating a method, in accordance with anembodiment of the disclosure;

FIG. 4 is a flow chart illustrating a method, in accordance with anembodiment of the disclosure;

FIG. 5 is a block diagram of a system, in accordance with an embodimentof the disclosure;

FIG. 6 is a plot of engine speed versus temperature, in accordance withan embodiment of the disclosure;

FIG. 7 is a plot of bleed valve position versus speed, in accordancewith an embodiment of the disclosure; and

FIG. 8 is a flow chart illustrating a method, in accordance with anembodiment of the disclosure.

DETAILED DESCRIPTION

A detailed description of one or more embodiments of the disclosedapparatus and method are presented herein by way of exemplification andnot limitation with reference to the Figures.

FIG. 1 schematically illustrates a gas turbine engine 20. The gasturbine engine 20 is disclosed herein as a two-spool turbofan thatgenerally incorporates a fan section 22, a compressor section 24, acombustor section 26 and a turbine section 28. The fan section 22 drivesair along a bypass flow path B in a bypass duct, while the compressorsection 24 drives air along a core flow path C for compression andcommunication into the combustor section 26 then expansion through theturbine section 28. Although depicted as a two-spool turbofan gasturbine engine in the disclosed non-limiting embodiment, it should beunderstood that the concepts described herein are not limited to usewith two-spool turbofans as the teachings may be applied to other typesof turbine engines including three-spool architectures.

The exemplary engine 20 generally includes a low speed spool 30 and ahigh speed spool 32 mounted for rotation about an engine centrallongitudinal axis A relative to an engine static structure 36 viaseveral bearing systems 38. It should be understood that various bearingsystems 38 at various locations may alternatively or additionally beprovided, and the location of bearing systems 38 may be varied asappropriate to the application.

The low speed spool 30 generally includes an inner shaft 40 thatinterconnects a fan 42, a low pressure compressor 44 and a low pressureturbine 46. The inner shaft 40 is connected to the fan 42 through aspeed change mechanism, which in exemplary gas turbine engine 20 isillustrated as a geared architecture 48 to drive the fan 42 at a lowerspeed than the low speed spool 30. The high speed spool 32 includes anouter shaft 50 that interconnects a high pressure compressor 52 and highpressure turbine 54. A combustor 56 is arranged in exemplary gas turbine20 between the high pressure compressor 52 and the high pressure turbine54. An engine static structure 36 is arranged generally between the highpressure turbine 54 and the low pressure turbine 46. The engine staticstructure 36 further supports bearing systems 38 in the turbine section28. The inner shaft 40 and the outer shaft 50 are concentric and rotatevia bearing systems 38 about the engine central longitudinal axis Awhich is collinear with their longitudinal axes.

The core airflow is compressed by the low pressure compressor 44 thenthe high pressure compressor 52, mixed and burned with fuel in thecombustor 56, then expanded over the high pressure turbine 54 and lowpressure turbine 46. The turbines 46, 54 rotationally drive therespective low speed spool 30 and high speed spool 32 in response to theexpansion. It will be appreciated that each of the positions of the fansection 22, compressor section 24, combustor section 26, turbine section28, and fan drive gear system 48 may be varied. For example, gear system48 may be located aft of combustor section 26 or even aft of turbinesection 28, and fan section 22 may be positioned forward or aft of thelocation of gear system 48.

The engine 20 in one example is a high-bypass geared aircraft engine. Ina further example, the engine 20 bypass ratio is greater than about six(6), with an example embodiment being greater than about ten (10), thegeared architecture 48 is an epicyclic gear train, such as a planetarygear system or other gear system, with a gear reduction ratio of greaterthan about 2.3 and the low pressure turbine 46 has a pressure ratio thatis greater than about five. In one disclosed embodiment, the engine 20bypass ratio is greater than about ten (10:1), the fan diameter issignificantly larger than that of the low pressure compressor 44, andthe low pressure turbine 46 has a pressure ratio that is greater thanabout five 5:1. Low pressure turbine 46 pressure ratio is pressuremeasured prior to inlet of low pressure turbine 46 as related to thepressure at the outlet of the low pressure turbine 46 prior to anexhaust nozzle. The geared architecture 48 may be an epicycle geartrain, such as a planetary gear system or other gear system, with a gearreduction ratio of greater than about 2.3:1. It should be understood,however, that the above parameters are only exemplary of one embodimentof a geared architecture engine and that the present disclosure isapplicable to other gas turbine engines including direct driveturbofans.

A significant amount of thrust is provided by the bypass flow B due tothe high bypass ratio. The fan section 22 of the engine 20 is designedfor a particular flight condition—typically cruise at about 0.8 Mach andabout 35,000 feet (10,688 meters). The flight condition of 0.8 Mach and35,000 ft (10,688 meters), with the engine at its best fuelconsumption—also known as “bucket cruise Thrust Specific FuelConsumption (‘TSFC’)”—is the industry standard parameter of lbm of fuelbeing burned divided by lbf of thrust the engine produces at thatminimum point. “Low fan pressure ratio” is the pressure ratio across thefan blade alone, without a Fan Exit Guide Vane (“FEGV”) system. The lowfan pressure ratio as disclosed herein according to one non-limitingembodiment is less than about 1.45. “Low corrected fan tip speed” is theactual fan tip speed in ft/sec divided by an industry standardtemperature correction of [(Tram ° R)/(518.7° R)]{circumflex over( )}0.5. The “Low corrected fan tip speed” as disclosed herein accordingto one non-limiting embodiment is less than about 1150 ft/second (350.5m/sec).

While the example of FIG. 1 illustrates one example of the gas turbineengine 20, it will be understood that any number of spools, inclusion oromission of the gear system 48, and/or other elements and subsystems arecontemplated. Further, rotor systems described herein can be used in avariety of applications and need not be limited to gas turbine enginesfor aircraft applications. For example, rotor systems can be included inpower generation systems, which may be ground-based as a fixed positionor mobile system, and other such applications.

A number of temperature and/or pressure sensors can be installed atvarious locations within the gas turbine engine 20. For example, ambienttemperature can be determined a station 60 in front of the fan section22. An interstage turbine temperature (ITT) can be determined at station62 between the high pressure turbine 54 and the low pressure turbine 46.An exhaust gas temperature (EGT) can be determined at station 64downstream of the low pressure turbine 46. The gas turbine engine 20 canalso include one or more particle sensors 66, which may be installed atan inlet of the low pressure compressor 44 of the gas turbine engine 20downstream of the fan 42 of the gas turbine engine 20. The gas turbineengine 20 can also include a plurality of bleeds 68 between the lowpressure compressor 44 and the high pressure compressor 52 of the gasturbine engine 20. The bleeds 68 (also referred to as 2.5 bleeds) caninclude a plurality of valves that are selectively opened to controloperational performance of the gas turbine engine 20 (e.g., venting agas path). In embodiments, the bleeds 68 can be used to rejectenvironmental particulates (e.g., dirt) during flight and prevent theenvironmental particulates from reaching the engine core (e.g.,combustor section 26). Embodiments, as further described herein, usedata from a variety of sources to optimize opening times of the bleeds68 to improve/maximize performance of fuel burn, time on wing, icerejection, dirt rejection, and margin for EGT and/or ITT duringoperation of the gas turbine engine 20.

FIG. 2 illustrates a dirt mitigation system 100 that includes a controlsystem 102 that can control opening of the bleeds 68 of the gas turbineengine 20 of FIG. 1. The control system 102 may also interface with fuelcontrols 104 to meter delivery of fuel to the combustor 56 of FIG. 1.The control system 102 can receive sensor data from various sensors,such as particle sensors 66, temperature sensors 106, speed sensors 107,pressure sensors 108, and/or other sensors (not depicted). Thetemperature sensors 106 and/or pressure sensors 108 can be located atvarious stations throughout the gas turbine engine 20, such as stations60, 62, 64 of FIG. 1, and other such locations. The speed sensors 107can detect the speed of various rotating components, such as the lowspeed spool 30, high speed spool 32, and/or fan 42. In some embodiments,the particle sensors 66 can be omitted, and particle data can bereceived or derived from other data sources, such as data received froman aircraft communication system 118. Other sensed parameters can bereceived on the aircraft communication system 118, such as an aircrafton-ground indicator (e.g., weight-on-wheels), aircraft altitude aboveground level, thrust commands, and other such values.

The control system 102 can include processing circuitry 110 and a memorysystem 112 to store data and instructions that are executed by theprocessing circuitry 110. The executable instructions may be stored ororganized in any manner and at any level of abstraction, such as inconnection with a controlling and/or monitoring operation of the dirtmitigation system 100 and/or other aspects of the gas turbine engine 20.The processing circuitry 110 can be any type or combination of centralprocessing unit (CPU), including one or more of: a microprocessor, adigital signal processor (DSP), a microcontroller, an applicationspecific integrated circuit (ASIC), a field programmable gate array(FPGA), or the like. Also, in embodiments, the memory system 112 mayinclude random access memory (RAM), read only memory (ROM), or otherelectronic, optical, magnetic, or any other computer readable mediumonto which is stored data and algorithms in a non-transitory form. Thecontrol system 102 is operable to access sensor data for use by controllogic 114 in the memory system 112, which may be executed by theprocessing circuitry 110 to control the bleeds 68 and/or fuel controls104. The control system 102 can include other interfaces (not depicted),such as various inputs, outputs, communication interfaces, powersystems, and the like. The control system 102 can also receive one ormore configuration parameters as input from a data storage unit 116 toenable, disable, and/or otherwise configure functionality of the controlsystem 102. Further, the control system 102 can write values back to thedata storage unit 116 for long-term storage and subsequent analysis.

Referring now to FIG. 3 with continued reference to FIGS. 1 and 2, FIG.3 is a flow chart illustrating a method 200 of dirt mitigation in a gasturbine engine 20, in accordance with an embodiment. The method 200 maybe performed, for example, by the dirt mitigation system 100 of FIG. 2.For purposes of explanation, the method 200 is described primarily withrespect to the dirt mitigation system 100; however, it will beunderstood that the method 200 can be performed on other configurations(not depicted).

At block 202, the control system 102 can determine a particulateingestion estimate indicative of dirt ingested in the gas turbine engine20. The particulate ingestion estimate can be determined based on aplurality of particle sensor data from the gas turbine engine 20, forinstance, as received from the particle sensors 66 or the aircraftcommunication system 118. In some embodiments, the particle sensor datamay be derived from a combination of observed environmental conditionsand look-up tables based on, for example, the location of the gasturbine engine 20 and an environmental parameter associated with thelocation. For instance, particulate tables may define particle datavalues observed in particular locations, at particular altitudes, andtime-of-year to estimate likely particulate ingestion as an aircraftthat includes the gas turbine engine 20 has an exposure time through theenvironment, where, for example, particle sensors 66 are unavailable ornon-operational.

At block 204, the control system 102 can determine one or more operatingparameters of the gas turbine engine 20. The one or more operatingparameters of the gas turbine engine 20 can include one or more of: aflight segment (e.g., take-off, climb, cruise, descent, thrust reverse),a fuel consumption rate, an operating margin of the gas turbine engine20, and/or other parameters.

At block 206, the control system 102 can alter a bleed control scheduleof the gas turbine engine 20 to purge at least a portion of the dirtingested in the gas turbine engine 20 through one or more bleeds 68 ofthe gas turbine engine 20 based on the particulate ingestion estimateand the one or more operating parameters. Altering of the bleed controlschedule can be further based on one or more of: an ambient airtemperature, an interstage turbine temperature, an exhaust gastemperature, a derate setting, a thrust specific fuel consumption of thegas turbine engine, and/or other values. The control system 102 canrevert to a default bleed control schedule of the gas turbine engine 20based on detection of a fault associated with the dirt mitigation system100, such as a failure of the particle sensors 66.

While the above description has described the flow process of FIG. 3 ina particular order, it should be appreciated that unless otherwisespecifically required in the attached claims that the ordering of thesteps may be varied.

Referring now to FIG. 4 with continued reference to FIGS. 1-3, FIG. 4 isa flow chart illustrating a method 300 of dirt mitigation in a gasturbine engine 20, in accordance with an embodiment. The method 300expands upon the method 200 of FIG. 3 as a further example. The method300 may be performed, for example, by the dirt mitigation system 100 ofFIG. 2. For purposes of explanation, the method 300 is describedprimarily with respect to the dirt mitigation system 100; however, itwill be understood that the method 300 can be performed on otherconfigurations (not depicted).

At block 302, the control system 102 can read particle sensor data todetermine a dirt concentration, which may be expressed, for example, asmilligrams per cubic meter or other such units of measurement. At block304, the control system 102 determines whether the particle sensor dataindicates that a dirt concentration is above a threshold that isconsidered a harmful dirt concentration, and if so, the method 300advances to block 306.

At block 306, the control system 102 can determine whether enginedeterioration is within a deterioration limit, and if so, the method 300advances to block 308. Engine deterioration can be quantified, forexample, by comparing measured temperatures at stations of the gasturbine engine 20, and comparing the results to expected values todetermine whether performance meets expected margins. Metal temperaturewithin the gas turbine engine 20 can increase as a function ofaccumulated dirt in combination with engine parameters and environmentaleffects. Dirt build-up increases backside resistance in a heat transfernetwork, which can yield a higher temperature as time goes on for agiven set of performance characteristics.

At block 308, the control system 102 determines whether the gas turbineengine 20 is within an operability limit prior to altering the bleedcontrol schedule, and if so, the method 300 advances to block 310.Operability limits can include constraints on when dirt rejection usingthe bleeds 68 can be performed. For example, if an aircraft thatincorporates the gas turbine engine 20 is heavily loaded (e.g., highweight) and it is a hot day (e.g., 105 degrees F.), then there may notbe sufficient margin to use the bleeds 68 for dirt rejection. However,if the ambient temperature is colder, (e.g., 40 degrees F.), there maybe enough margin to support opening of the bleeds 68 for dirt rejectionwithout safety concerns or excessive fuel burn. Thus, there is a balancebetween dirt level, performance reduction aspects, and operabilityimpact in determining when to open bleeds 68 to reject dirt at block310.

After opening the bleeds 68 to reject dirt at block 310, at block 312,the control system 102 can determine an amount of dirt in the enginecore. Dirt accumulation can be determined based on particle sensor datasince a last cleaning event. Opening of the bleeds 68 can reject aportion of the dirt according to a rejection efficiency. At block 313, atotal amount of ingested dirt since assembly can be computed, forexample, by computing sensed dirt and adjusting for bleed purgingeffects since the gas turbine engine 20 was assembled and/or fullycleaned. At block 314, usage-based lifing computations can determine theimpact of dirt reduction associated with purging at least a portion ofthe dirt ingested in the gas turbine engine 20, such as future servicingof components within the gas turbine engine 20. Usage based lifing cantrack durability modes effecting time on wing due to environmentalimpacts from sources such as salt, fine dirt, dust, and other particles.Lifing durability modes can include, for example, corrosion of alloysand coatings, oxidation, calcium-magnesium-aluminum-silicon attack ofthermal barrier coatings, and stress corrosion cracking. The lifingdurability modes can be temperature and environmental effect dependent.Damage related to each mode can be computed at time intervals for eacheffected part of the gas turbine engine 20. The summation of time pointscan be performed using Miner's rule, for instance, as a cumulativedamage model to determine life used up until the current time (e.g.,usage based life).

Returning to block 304, if the control system 102 determines that theparticle sensor data indicates that a dirt concentration is below thethreshold, at block 316, the control system 102 can maintain the bleedcontrol schedule to maximize fuel economy. At block 317, the controlsystem 102 can determine a total amount of dirt ingested using particlesensor data. At block 318, usage-based lifing can be performed todetermine component servicing without regard to dirt. Usage-based lifingcan use total dirt data up to the time of the lifing calculations andadjust temperature effects due to dirt ingested, if needed to accountfor dirt accumulation and purging effects.

At block 306 if the engine deterioration is outside of the deteriorationlimit, or at block 308, if the gas turbine engine 20 is outside of theoperability limit, then the method 300 advances to block 320. At block320, the control system 102 can maintain the bleed control schedule tomaximize fuel economy. At block 322, one or more usage-based lifingcomputations can be performed to determine a time on wing for full dirtimpact. At block 324, a summation of flight data (e.g., from blocks 314,318, 322) can be used to calculate time on wing and project a nextmaintenance action needed for the gas turbine engine 20 based on thedirt impact. The buildup of dirt data can be used in combination withengine parameters, such as compressor exit temperature, pressure, fuelair ratio, combustor exit temperature, and other such parameters todetermine lifing effects and determine when cleaning, inspection, orother servicing will likely be needed. Total dirt data can be used todebit life at a given temperature across durability modes. As the amountof dirt increases during each time interval, the time it takes at agiven temperature for thermal barrier coatings to spall can decrease,the time to corrode can decrease, and the time to oxidize can decrease.

While the above description has described the flow process of FIG. 4 ina particular order, it should be appreciated that unless otherwisespecifically required in the attached claims that the ordering of thesteps may be varied.

FIG. 5 depicts a system 400 that can be incorporated as part of the dirtmitigation system 100 of FIG. 2. For example, dirt rejection mode logic402 may be activated in a dirt rejection mode as part of the controllogic 114 of FIG. 2. The dirt rejection mode logic 402 can be enabled ordisabled based on a selection 404 of the data storage unit 116 of FIG. 2or an alternate input source (not depicted). The selection 404 of thedata storage unit 116 can also include one or more configurationparameters of the dirt rejection mode logic 402, such as thresholdvalues, offsets, default values, and other such values. The dirtrejection mode logic 402 can define one or more activation conditions406 that result in one or more commands 408 to adjust a bleed controlschedule of the gas turbine engine 20 of FIG. 1. The dirt rejection modelogic 402 can also define one or more deactivation conditions 410 thatresult changing or halting the one or more commands 408 to restore thebleed control schedule of the gas turbine engine 20 and/or fully closethe bleeds 68.

In embodiments, the one or more activation conditions 406 can enable thecontrol system 102 of FIG. 2 to adjust the bleed control schedule of thegas turbine engine 20 to extend a time to hold the one or more bleeds 68of the gas turbine engine 20 partially open at a power setting above athreshold based on the one or more activation conditions 406. The one ormore activation conditions 406 can leverage aircraft fleet historicaldata in setting the threshold and other parameters according to typicalderating of a maximum takeoff thrust setting under a variety ofoperating conditions.

FIGS. 6 and 7 illustrate derating and example plots 500, 600 relative toholding the one or more bleeds 68 partially open. Opening of bleeds 68can be limited, for example, by engine speed and engine temperature.Conditions under which an aircraft needs to achieve a full maximumtakeoff thrust setting 502 can depend on aircraft weight, temperatureconditions, and other factors (e.g., component damage). Where anaircraft is not fully loaded to maximum weight capacity, for instance, aderated thrust setting 504 can be used, where a lower power level andengine speed of the gas turbine engine 20 of FIG. 1 may be sufficientfor achieving takeoff power of an aircraft. As temperature rises,operating temperature margins can be reduced. A full-rated hot day limit506 can define an outer limit that restricts a maximum engine speed astemperature increases. A thermal pinch point 508 is defined at anintersection of the full maximum takeoff thrust setting 502 and thefull-rated hot day limit 506. The derated thrust setting 504 alsoresults in a corresponding derated hot day limit 510. A bleed openregion 512 is bounded by the derated thrust setting 504 and the deratedhot day limit 510, where the one or more bleeds 68 can be opened. Ableed closed region 514 is defined as an area outside of the bleed openregion 512, where the one or more bleeds 68 are closed for maximizingperformance of the gas turbine engine 20.

As illustrated in plot 600, bleeds 68 of FIG. 1 can transition from afully opened position 602 at lower speeds and ramp 604 towards a fullyclosed position 606 at higher speeds of the gas turbine engine 20 ofFIG. 1. Rather than fully closing the bleeds 68 at a power setting abovea threshold 608, the one or more bleeds 68 can be held in a partiallyopen position 610 such that dirt can be rejected at a higher powersetting, for instance during takeoff where dirt is more likely to beingested. As one example, the partially open position 610 can be aboutsix percent open. Derating below a full maximum takeoff thrust setting612, such as a ten percent derating 614 or a twenty percent derating 616can provide temperature margin as a maximum temperature is limited to areduced value at lower engine speeds. Keeping one or more bleeds 68 inthe partially open position 610 can trade ITT margin for dirt rejection.

Referring now to FIG. 8 with continued reference to FIGS. 1-7, FIG. 8 isa flow chart illustrating a method 700 of adaptive bleed scheduleadjustment in gas turbine engine 20, in accordance with an embodiment.The method 700 may be performed, for example, by the dirt mitigationsystem 100 of FIG. 2 and the system 400 of FIG. 5. For purposes ofexplanation, the method 700 is described primarily with respect to thedirt mitigation system 100; however, it will be understood that themethod 700 can be performed on other configurations (not depicted).

At block 702, the control system 102 checks one or more activationconditions 406 of a dirt rejection mode of dirt rejection mode logic 402in the gas turbine engine 20. The dirt rejection mode can be activatedbased on meeting all of the one or more activation conditions 406 (e.g.,a logical AND). The one or more activation conditions 406 can includedetecting that the gas turbine engine 20 is incorporated in an aircrafton the ground (e.g. weight-on-wheels equals TRUE), and an engine speedcommand of the gas turbine engine 20 is less than a full maximum takeoffthrust setting 502 with a thrust margin. The thrust margin can establisha limit as a derated thrust setting 504. The one or more activationconditions 406 can include confirming that the gas turbine engine 20 isnot located in a production test cell, which may be determined based onan input value or an operating mode of the control system 102. One ormore configuration parameters of the dirt rejection mode can be setresponsive to an input from the data storage unit 116 to the controlsystem 102.

At block 704, the control system 102 can adjust a bleed control scheduleof the gas turbine engine 20 to extend a time to hold one or more bleeds68 of the gas turbine engine 20 partially open at a power setting abovea threshold 608 based on the one or more activation conditions 406, forinstance, in a partially open position 610 as part of the commands 408.The control system 102 can be further configured to adjust a powersetting of the gas turbine engine 20 to compensate for holding the oneor more bleeds 68 of the gas turbine engine 20 partially open (e.g.,increase a thrust setting by about 6 RPM). Adjusting the bleed controlschedule may be further based on one or more of: an ambient airtemperature, an interstage turbine temperature, an exhaust gastemperature, a derate setting, an engine speed, and a thrust specificfuel consumption of the gas turbine engine 20.

At block 706, the control system 102 can check one or more deactivationconditions 410 of the dirt rejection mode of dirt rejection mode logic402 in the gas turbine engine 20. At block 708, the control system 102can deactivate the dirt rejection mode to fully close the one or morebleeds 68 based on the one or more deactivation conditions 410. The oneor more deactivation conditions 410 can include, for example,determining that an altitude of the aircraft is above an altitudethreshold, determining that a time since activation is greater than atime threshold, and/or determining that the engine speed command of thegas turbine engine 20 is greater than the full maximum takeoff thrustsetting with the thrust margin. The altitude threshold may default to avalue of about 1500 feet above ground level, and the time threshold maydefault to a value of about three minutes to cover early takeoffconditions where higher dirt levels may be expected. Further, the one ormore deactivation conditions 410 can include determining that ago-around mode is active and/or determining that a synthesizedinterstage turbine temperature is greater than a temperature threshold.The go-around mode may be set where an aircraft landing sequence isaborted on final approach, for instance. The synthesized interstageturbine temperature can be a modeled value of ITT to verify thatadequate temperature margin exists while the bleeds 68 are in thepartially open position 610. The temperature threshold can be definedwith respect to the thermal pinch point 508 depending on the currentderate setting.

The term “about” is intended to include the degree of error associatedwith measurement of the particular quantity based upon the equipmentavailable at the time of filing the application.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the presentdisclosure. As used herein, the singular forms “a”, “an” and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise. It will be further understood that the terms“comprises” and/or “comprising,” when used in this specification,specify the presence of stated features, integers, steps, operations,elements, and/or components, but do not preclude the presence oraddition of one or more other features, integers, steps, operations,element components, and/or groups thereof.

While the present disclosure has been described with reference to anexemplary embodiment or embodiments, it will be understood by thoseskilled in the art that various changes may be made and equivalents maybe substituted for elements thereof without departing from the scope ofthe present disclosure. In addition, many modifications may be made toadapt a particular situation or material to the teachings of the presentdisclosure without departing from the essential scope thereof.Therefore, it is intended that the present disclosure not be limited tothe particular embodiment disclosed as the best mode contemplated forcarrying out this present disclosure, but that the present disclosurewill include all embodiments falling within the scope of the claims.

What is claimed is:
 1. A dirt mitigation system for a gas turbineengine, the dirt mitigation system comprising: a plurality of bleeds ofthe gas turbine engine; and a control system configured to: determine aparticulate ingestion estimate indicative of dirt ingested in the gasturbine engine; determine one or more operating parameters of the gasturbine engine; and alter a bleed control schedule of the gas turbineengine to purge at least a portion of the dirt ingested in the gasturbine engine through one or more of the bleeds of the gas turbineengine based on the particulate ingestion estimate and the one or moreoperating parameters.
 2. The dirt mitigation system of claim 1, whereinthe particulate ingestion estimate is determined based on a plurality ofparticle sensor data from the gas turbine engine.
 3. The dirt mitigationsystem of claim 2, wherein the particle sensor data is received from oneor more particle sensors at an inlet of a low pressure compressor of thegas turbine engine downstream of a fan of the gas turbine engine.
 4. Thedirt mitigation system of claim 2, wherein the control system is furtherconfigured to determine whether the particle sensor data indicates thata dirt concentration is above a threshold, an engine deterioration iswithin a deterioration limit, and the gas turbine engine is within anoperability limit prior to altering the bleed control schedule.
 5. Thedirt mitigation system of claim 4, wherein the control system is furtherconfigured to determine an amount of dirt in the gas turbine engine anddetermine an impact of dirt reduction associated with purging at leastthe portion of the dirt ingested in the gas turbine engine.
 6. The dirtmitigation system of claim 5, wherein the control system is furtherconfigured to maintain the bleed control schedule to maximize fueleconomy based on determining that the dirt concentration is below thethreshold, the engine deterioration is outside of the deteriorationlimit, or the gas turbine engine is outside of the operability limit. 7.The dirt mitigation system of claim 6, wherein the control system isfurther configured to perform one or more usage-based lifingcomputations to determine a dirt impact on the gas turbine engine andproject a next maintenance action needed for the gas turbine enginebased on the dirt impact.
 8. The dirt mitigation system of claim 1,wherein the bleeds are between a low pressure compressor and a highpressure compressor of the gas turbine engine.
 9. The dirt mitigationsystem of claim 1, wherein altering of the bleed control schedule isfurther based on one or more of: an ambient air temperature, aninterstage turbine temperature, an exhaust gas temperature, a deratesetting, and a thrust specific fuel consumption of the gas turbineengine.
 10. The dirt mitigation system of claim 1, wherein the one ormore operating parameters of the gas turbine engine comprise one or moreof: a flight segment, a fuel consumption rate, and an operating marginof the gas turbine engine.
 11. The dirt mitigation system of claim 1,wherein the particulate ingestion estimate is determined based on alocation of the gas turbine engine and an environmental parameterassociated with the location.
 12. The dirt mitigation system of claim 1,wherein the control system is further configured to revert to a defaultbleed control schedule of the gas turbine engine based on detection of afault associated with the dirt mitigation system.
 13. A method of dirtmitigation in a gas turbine engine, the method comprising: determining aparticulate ingestion estimate indicative of dirt ingested in the gasturbine engine; determining one or more operating parameters of the gasturbine engine; and altering a bleed control schedule of the gas turbineengine to purge at least a portion of the dirt ingested in the gasturbine engine through one or more bleeds of the gas turbine enginebased on the particulate ingestion estimate and the one or moreoperating parameters.
 14. The method of claim 13, wherein theparticulate ingestion estimate is determined based on a plurality ofparticle sensor data from the gas turbine engine, and the method furthercomprises: determining whether the particle sensor data indicates that adirt concentration is above a threshold, an engine deterioration iswithin a deterioration limit, and the gas turbine engine is within anoperability limit prior to altering the bleed control schedule;determining an amount of dirt in the gas turbine engine; and determiningan impact of dirt reduction associated with purging at least the portionof the dirt ingested in the gas turbine engine.
 15. The method of claim14, further comprising: maintaining the bleed control schedule tomaximize fuel economy based on determining that the dirt concentrationis below the threshold, the engine deterioration is outside of thedeterioration limit, or the gas turbine engine is outside of theoperability limit.
 16. The method of claim 15, further comprising:performing one or more usage-based lifing computations to determine adirt impact on the gas turbine engine and project a next maintenanceaction needed for the gas turbine engine based on the dirt impact. 17.The method of claim 13, wherein altering of the bleed control scheduleis further based on one or more of: an ambient air temperature, aninterstage turbine temperature, an exhaust gas temperature, a deratesetting, and a thrust specific fuel consumption of the gas turbineengine.
 18. The method of claim 13, wherein the one or more operatingparameters of the gas turbine engine comprise one or more of: a flightsegment, a fuel consumption rate, and an operating margin of the gasturbine engine.
 19. The method of claim 13, wherein the particulateingestion estimate is determined based on a location of the gas turbineengine and an environmental parameter associated with the location. 20.The method of claim 13, further comprising: reverting to a default bleedcontrol schedule of the gas turbine engine based on detection of a faultassociated with the dirt mitigation system.